@type t() :: %OpenXchangeClient.Model.AppointmentFreeBusyItem{
categories: String.t() | nil,
color_label: integer() | nil,
confirmations: [OpenXchangeClient.Model.TaskConfirmation.t()] | nil,
created_by: String.t() | nil,
creation_date: integer() | nil,
end_date: integer() | nil,
folder_id: String.t() | nil,
full_time: boolean() | nil,
id: String.t() | nil,
lastModifiedOfNewestAttachmentUTC: integer() | nil,
last_modified: integer() | nil,
modified_by: String.t() | nil,
number_of_attachments: integer() | nil,
participants: [OpenXchangeClient.Model.TaskParticipant.t()] | nil,
private_flag: boolean() | nil,
recurrence_type: integer() | nil,
shown_as: integer() | nil,
start_date: integer() | nil,
title: String.t() | nil
}